Processing masses of substantially organic material into shaped products and articles shaped accordingly

Abstract

Shaped articles in thin-walled form, such as threads, membranes, sheets and tubes and particularly material for encasing sausage, are produced from a shapable mass containing in aqueous dispersion at least one coagulable, amphoteric high molecular organic substance, such as collagen or other coagulable animal protein, by extruding the mass through a die into an aqueous bath in which coagulation of such substance in the extrudate is effected by changing the pH of the dispersion so that the isoelectric point of the substance is traversed, the dispersion being prepared with a sufficient content of polyvalent ions, such as calcium ions, to inhibit formation in the extrudate of a barrier to ion penetration. The dispersion desirably also contains an agent for cross-linking the coagulable substance in the extrudate. The mass fed to the extruding die preferably is a collagen paste containing glyoxal and calcium ions. The speed of the coagulation can be enhanced by subjecting the extrudate in the bath to a D.C. electric field.

I claim: 
     
       1. A process for producing shaped thin-walled articles from a shapable mass containing in aqueous dispersion at least one coagulable amphoteric high molecular organic substance such as coagulable animal protein, which comprises extruding the mass through a die that shapes it into the desired thin-walled form, passing the extrude into an aqueous coagulating bath; said dispersion having a pH to one side of the isoelectric point of said substance, and containing sufficient polyvalent ions to inhibit swelling of said substance and formation in the extrudate of an ion-selective barrier against ion penetration; said bath having a pH to the opposite side of said isoelectric point and being substantially free of salt other than at most a small amount of non-dehydrating salt; and in said bath coagulating said substance in the extrudate by effecting a change in the pH of said dispersion such that the isoelectric point of said substance is traversed with a change of the state of charge on the particles thereof. 
     
     
       2. A process according to claim 1, said dispersion being acidic and said bath consisting essentially of a dilute solution of a hydroxide. 
     
     
       3. A process according to claim 1, said dispersion being basic and said bath consisting essentially of a dilute acid solution. 
     
     
       4. A process according to claim 2, said substance comprising collagen and said dispersion also containing a cross-linking agent for the collagen that is inactive in the dispersion per se but is activated in the extrudate by contact with said bath. 
     
     
       5. A process according to claim 4, said cross-linking agent being a dialdehyde. 
     
     
       6. A process for producing shaped thin-walled articles from a shapable mass containing in aqueous dispersion at least one coagulable amphoteric high molecular organic substance such as coagulable animal protein, which comprises extruding the mass through a die that shapes it into the desired thin-walled form, and in said bath coagulating said substance in the extrudate by effecting a change in the pH of said dispersion such that the isoelectric point of said substance is traversed, said dispersion containing sufficient polyvalent ions to inhibit formation in the extrudate of a barrier against ion penetration; said dispersion being acidic and said bath consisting essentially of a dilute solution of a hydroxide; said substance comprising collagen and said dispersion also containing a cross-linking agent for the collagen that is inactive in the dispersion per se but is activated in the extrudate by contact with said bath; said cross-linking agent being glyoxal. 
     
     
       7. A process according to claim 4, said polyvalent ions being calcium ions. 
     
     
       8. A process for producing shaped thin-walled articles from a shapable mass containing in aqueous dispersion at least one coagulable amphoteric high molecular organic substance such as coagulable animal protein, which comprises extruding the mass through a die that shapes it into the desired thin-walled form, passing the extrude into an aqueous coagulating bath; and in said bath coagulating said substance in the extrudate by effecting a change in the pH of said dispersion such that the isoelectric point of said substance is traversed, said dispersion containing sufficient polyvalent ions to inhibit formation in the extrudate of a barrier against ion penetration, said dispersion being acidic and said bath consisting essentially of a dilute solution of a hydroxide, said substance comprising collagen and said dispersion containing about 0.01-0.2 mols of calcium ion per liter and about 0.05-0.5% by weight of glyoxal. 
     
     
       9. A process according to claim 2, or 8, said bath being an alkaline solution containing about 0.01 to about 1.0 mol of NaoH per liter. 
     
     
       10. A process according to claim 1, 2, 3, 4, 7, or 8, said extrudate being passed vertically upward from said die into said bath. 
     
     
       11. A process according to claim 10, and keeping said bath separate from said die by a layer of a liquid that is inert both to the bath and to the extrudate and is imiscible with and of higher specific gravity than the liquid of said bath. 
     
     
       12. A process according to claim 1, 2, 3, 4, 7, or 8, and subjecting the extrudate in said bath to a D.C. electric field applied transverse to the wall of the extrudate. 
     
     
       13. A process for producing sausage casings or like tubular products, which comprises forming a shapable acidic collagen paste containing about 2 to 6% by weight of collagen, about 0.01 to 0.2 mols of calcium ion per liter and about 0.05 to 0.5% by weight of glyoxal; extruding said paste through a die that shapes it into a thin-walled seamless tubular form; passing the extrudate from said die into a bath consisting essentially of a dilute aqueous solution of a hydroxide; and by the action of said bath effecting a change in the pH of the extrudate sufficient to change the state of charge on the particles thereof and cause reaction of the glyoxal therein, so as to coagulate and cross-link the collagen in the extrudate. 
     
     
       14. A process according to claim 13, said extrudate being passed vertically upward from said die into said bath. 
     
     
       15. A process according to claim 14, and as the extrudate is being formed and passed into said bath introducing a gas stream inside its tubular wall to keep it inflated and exposed both inside and outside to coagulating action. 
     
     
       16. A process according to claim 15, said gas stream containing ammonia for neutralizing the extrudate. 
     
     
       17. A process according to claim 13, 14, 15, or 16, and subjecting the extrudate in said bath to a D.c. electric field applied transverse to the wall of the extrudate. 
     
     
       18. Shaped thin-walled articles such as threads, membranes, sheets, or tubes, formed as extrudates of an aqueous dispersion containing and having coagulated therein in situ at least one amphoteric high molecular organic substance such as amphoteric animal protein, as produced by a process according to claim 1, 2, 3, 4, 7, or 8. 
     
     
       19. Shaped tubular articles suited for use as sausage casings, formed as extrudates of a collagen paste having the collagen therein coagulated in situ, as prepared by a process according to claim 1, 2, 3, 4,7,8, 13, 14, 15, 16, or 17. 
     
     
       20. Shaped tubular articles suited for use as sausage casings, formed as extrudates of a collagen paste containing calcium ions and glyoxal and having the collagen therein coagulated and cross-linked in situ.